When All the World’s a City

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More than half the world’s population now lives in cities: Old ones are growing, new ones are emerging, and—especially in the developing world—urban areas are expanding dramatically. This map superimposes a projected 2020 urban landscape on the 1990 one, while highlighting some present-day statistics.

Megacities create enormous environmental, social, and infrastructure challenges, but they can also stimulate business, offering myriad opportunities for innovation and entrepreneurship.

A version of this article appeared in the June 2012 issue of Harvard Business Review.